The present invention relates in general to a powertrain housing and in particular to a powertrain housing configured to receive a torque roll restrictor or torque rod.
Automotive powertrains, which may comprise an engine and transaxle, utilize powertrain torque roll restrictors or torque rods to prevent unwanted rotation of the engine and transaxle about an axis which, if not coincidental with the engine's crankshaft centre axis, is at least parallel thereto. Known automotive powertrain roll restrictors utilize brackets for attaching the restrictor to the transaxle or engine.
In this regard, FIG. 1 shows a roll restrictor system for an automotive powertrain 10, which was previously disclosed in U.S. Pat. No. 8,215,444, which is incorporated herein by reference. The powertrain 10 has an engine 14 and a transaxle 18 with a longitudinal center line A. The powertrain 10 also includes a roll restriction system. The transaxle 18 includes a first mounting pad 22 to which a mounting bracket 26 is attached. A control link 42 connects bracket 26 to a vehicle structural member 46.
A powertrain torque roll restrictor has many functions. It needs to simultaneously isolate engine excitation forces at both idle (small force preloads) and wide open throttle (large force preloads), whilst controlling powertrain roll during highly transient dynamic events. These conflicting requirements require a part that allows sufficient displacement with a low rate of change of stiffness.
As depicted in FIG. 2, a previously-proposed powertrain torque roll restrictor 120 may comprise a core 143 that is attached to a vehicle sub-frame, e.g. via a link bolt 142; and a housing 144 that is resiliently coupled to the core 143. The housing 144 is in turn connected to a mounting bracket 126 via a bolt 128. The mounting bracket 126 is bolted to the transmission clutch housing 118 via two or more further bolts 130, 132.
However, because of package constraints, it is difficult to arrange the joint between the mounting bracket 126 and the transmission clutch housing 118 in an orientation which allows the bolts 130, 132 to work in tension in one plane. Accordingly, the bolts 130, 132 are often in two planes with at least one of the bolts 130, 132 working in shear. The combination of the shear loads and the clamp loss due to gap tolerances created by the two planes can lead to joint slip and joint relaxation when subjected to the high dynamic loads resulting in torque loss and the failure of the joint.